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These animated cases are an incredible learning resource. A picture is worth a thousand words but a cool animation is worth a thousand pictures. I spent years
by beachy 5y ago
These animated cases are an incredible learning resource. A picture is worth a thousand words but a cool animation is worth a thousand pictures.
I spent years repairing IBM rotating chain mainframe printers (1403) in the field in the 80s, and I never really understood what I was doing. When I saw Ken Shirriff's animation of how hammer timing works, I instantly got it.
http://ibm-1401.info/KenShirriff-1403Animation.html http://ibm-1401.info/KenShirriff-1403Animation.html
- kens 5y agoThanks! That animation was mainly to help me understand the chain printer timing myself. If it helps anyone else, that's a bonus :-) The quick summary is that the characters are on a rotating chain, and the printer has 132 hammers, one for each column. When the character lines up with the column the hammer fires. Thus, a whole line is printed very fast. This sounds straightforward, but the implementation is surprisingly tricky to make it optimized. The complicated part is the vernier spacing between the chain and the hammers, so one hammer lines up at a time, and this timing is synchronized with the core memory access speed so the computer can check the character in the print buffer at that position at the right time.
- beachy 5y agoI have happy memories of printing lines of HHHHHH characters and tweaking hammer timings to get each character to print on both sides. Not to mention getting squirted from hot hydraulic fluid. Well, not really happy come to think of it :) If you've had any experience Ken with 3890 check sorters, those were true electromechanical marvels.
- kens 5y agoI don't have any experience with check sorters, but I do have experience with replacing hydraulic fluid in the printer :-) The museum in Binghamton, NY has an IBM 1255 check sorter, which is puny in comparison to the 3890, which is a long, long, long machine.